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The terms "drug abuse" and "drug addiction" are often used interchangeably, but in fact, they denote very different conditions. The term "drug abuse" refers to the use of a substance in a manner that deviates from the culturally acceptable norms, while the term "drug addiction" describes a disorder where the drug appears to be the dominant influence on the individual's behavior. More specially, drug addiction is behavioral syndrome where the individual’s motivation is dominated by the procurement and use of a drug and where the normal constraints on the individual’s behavior are largely ineffective (Bozarth, 2009; see also Bozarth, 1990). This condition may or may not be accompanied by physical dependence, but it does seem to be invariably accompanied by psychological dependence. Psychological dependence, however, is NOT equivalent to addiction. Psychological dependence, like its physical dependence counterpart, simply means that the individual requires the substance for normal psychological functioning. That is, abstinence from the substance produces withdrawal reactions that disrupt normal psychological (or in the case of physical dependence, physiological) function. Of course psychological dependence has an underlying neurophysiological basis; therefore the syndrome describing disturbances in normal physiological function other than psychological aspects (such as disturbances in autonomic nervous system producing nausea, chills, tremors, etc.) are better denoted as physical dependence and withdrawal. There are undoubtedly cases of psychological dependence without addiction to the substance—the substance is necessary for ‘normal’ psychological functioning, but the motivation to obtain the substance is insufficiently strong to constitute an addiction to that substance (e.g., daily caffeine use for many people).

There are many cases where the use of a substance constitutes drug abuse but not addiction. For example, any use of an illicit substance is considered drug abuse even if the substance is used only rarely and the individual retains control of their substance use. There are even numerous cases where the individual seems to loose control of their substance use, but it still doesn’t constitute true addiction to that substance (see below). Drug abuse is defined by the society in which it exists; what is considered drug abuse in one culture may be perfectly acceptable in another. Drug abuse does not necessarily imply that the motivation to continue use of the substance is strong.

The causes of drug addiction and of drug abuse are often quite different. Drug addiction, although the more intense motivational condition, is actually less complex than is drug abuse. Drug addiction involves the drug’s action on brain reward and motivation systems whereby it produces neurochemical disturbances that result in the drug becoming the dominant motivational factor for the individual. This involves an “incentive contrast” where there is a dramatic increase in the incentive value or attraction to the drug reward and a marked decrease in the incentive value or interest in other, normal rewards (Bozarth, 2009). The ensuing motivational toxicity is a characteristic of addiction that requires no pre-existing conditions or special personality types—simply the neurochemical action of certain (i.e., addictive) drugs on brain reward systems.

Drug abuse, on the other hand, involves the ‘misuse’ of a substance (according to social norms) that may or may not be accompanied by a strong motivation to continue the use of the substance. In cases where drug abuse appears to be strongly motivated, the motivation actually depends on characteristics of the individual or of the social setting to produce these strong motivational effects. That is, apparent “addictiveness” in cases of strongly motivated drug abuse without addiction does not actually involve an attribute of the drug per se. Rather, some set of psychosocial factors account for the strong motivation to engage in substance abuse. In many cases of pathological drug abuse where the motivation to continue the substance use seems strongly motivated, other psychiatric disturbances are present. These comorbid disorders are much different than actual addiction to the substance and need to be carefully distinguished from true drug addiction when considering the appropriate treatment approach.

There are obviously many cases of drug abuse that do not constitute drug addiction. In contrast, most cases of drug addiction involve drug abuse; however, there are even a few cases where drug addiction does not constitute drug abuse such as prescribed high-dose opiate medication for chronic pain.

Determining whether the use of an illicit substance constitutes simply drug abuse or true drug addiction can seem daunting, but it’s actually quite simple. If the substance use is intensely motivated as is inherent in the definition of addiction AND if the motivation for the substance use arises from its action directly on brain reward systems, it constitutes drug addiction. If special, pre-existing psychosocial factors are necessary for the substance use to develop (regardless of how strongly that behavior seems to be), then it constitutes drug abuse which involves more than just the substance’s action on brain reward systems and therefore is not truly an addiction to that substance. In cases of compulsive drug abuse comorbid disorders are very likely to be present.

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